Transformation of Cochliobolus lunatus with pUT 720 changes the steroid hydroxylating ability of the fungus

Cytochrome P450 enzyme systems in fungi

The involvement of cytochrome P450 enzymes in many complex fungal bioconversion processes has been characterized in recent years. Accordingly, there is now considerable scientific interest in fungal cytochrome P450 enzyme systems. In contrast to S. cerevisiae, where surprisingly few P450 genes have been identified, biochemical data suggest that many fungi possess numerous P450 genes. This review summarizes the current information pertaining to these fungal cytochrome P450 systems, with emphasis on the molecular genetics. The use of molecular techniques to improve cytochrome P450 activities in fungi is also discussed.

11Beta-hydroxysteroid dehydrogenase activity in progesterone biotransformation by the filamentous fungus Cochliobolus lunatus

Progesterone biotransformation was examined in relation to hydroxylating and dehydrogenating enzymes of Cochliobolus lunatus. 11beta-hydroxysteroid dehydrogenase activity (11beta-HSD) was located in cytosolic fraction and was NADP-dependent, inducible by progesterone and apparently uni-directional. Several inhibitors of 11beta-hydroxysteroid dehydrogenase were tested; furosemide, glycyrrhizic-acid and carbenoxolone did not influence the dehydrogenation of 11beta-hydroxy-4-pregnene-3,20-dione to 4-pregnene-3,11,20-trione, although grapefruit juice significantly reduced the rate of progesterone hydroxylation.

Progesterone metabolism by the filamentous fungus Cochliobolus lunatus

Studies of Cochliobolus lunatus m118 steroid metabolism by thin-layer chromatography, mass spectrometry and NMR spectroscopy revealed that the fungus hydroxylates progesterone at positions 7 alpha, 11 beta and 14 alpha, and oxidizes the 11 beta-hydroxy group to the ketone. The 1H NMR spectra of two of the steroid metabolites, 11 beta,14 alpha-dihydroxyprogesterone and 11-oxo-14 alpha-hydroxyprogesterone, are reported for the first time. It is still not known if all the hydroxylation reactions are performed in C. lunatus by a single, non-specific, steroid hydroxylase, structurally different from the 11 beta-hydroxylase found in higher eucaryotes, or if different forms of the enzyme are involved.